Preheat the oven to 350°F. Wrap potatoes in aluminum foil, and bake for 40–50 minutes until tender. Peel while warm and transfer them to a bowl. Using a fork, crush the potatoes with the canned tuna, crème fraîche, olives, olive oil, tomatoes, chives, vinegar, thyme, and lemon zest; season with salt and pepper.

Bring a large pot of salted water to a boil. Add the leeks and blanch until tender, about 5 minutes. Drain and pat dry. Put a large piece of plastic wrap on a flat work surface. Arrange the leeks in vertical rows, slightly overlapping, to form a 5-inch square. Spread the crushed potato mixture over the leeks, leaving a ½-inch border. If you are using the fresh tuna, put one stick horizontally across the center of the square. Using the plastic wrap, tightly roll the leeks away from you to form a log. Twist and tie the ends of the plastic wrap. Repeat with the remaining ingredients to form 4 rolls in all. Refrigerate rolls for 2 to 3 hours, unwrap, and cut with an electric or sharp knife into ½-inch-thick slices. Makes about 40 hors d'oeuvres.

Combine the julienned daikon radish with 2 tablespoons mayonnaise, chives, and mustard; season with salt and pepper and refrigerate. Combine the crab with the remaining mayonnaise and horseradish; season with salt, pepper, and Tabasco. Refrigerate.

Using a mandoline, cut the halved daikon radish lengthwise into very thin slices. Arrange the radish slices in vertical rows, slightly overlapping, on a large piece of plastic wrap, to form a 5-inch square. Dot the daikon with one quarter of the cilantro leaves. Arrange one quarter of the cucumber and carrots over a third of the square, leaving a ½-inch margin on the bottom edge. Spread one quarter of the radish remoulade and one quarter of the crab on top. Roll, repeat, and refrigerate, as with the tuna rolls. Unwrap and cut into ¾-inch-thick slices. Makes about 24 hors d'oeuvres.

Cook the asparagus in a pot of boiling salted water for 2 to 3 minutes. Drain under cold running water and then pat dry.

Heat olive oil in a skillet over medium-high heat. Add the mushrooms, shallot, garlic, and thyme, season with salt and pepper, and cook until almost all the liquid in the pan has evaporated, 12 to 15 minutes. Discard the garlic and thyme. When cool enough to handle, chop mushrooms finely. Mix in the cheeses and chives; taste and season if needed. (This can be prepared up to 1 day ahead.)

Preheat the oven to 400°F. Put a spring roll wrapper on a flat surface and brush with melted butter. Spread with one quarter of the mushroom mixture, leaving a ½-inch border. Put 1 asparagus horizontally across the mushrooms and roll up. Brush the outside of the roll with more melted butter. Repeat with the remaining ingredients. Bake rolls for 6 to 7 minutes until crisp and golden, turning them once. Cut into ¾-inch-thick slices with an electric or very sharp knife and serve immediately. Makes about 24 hors d'oeuvres.